#include<stdio.h>

int main()
{
    int start, end;
    int start_hour, start_min, end_hour, end_min;
    int dur, hh, mm;
    scanf("%d %d",&start, &end);
    start_hour = start/100;
    start_min = start%100;
    start = 60*start_hour + start_min;
    end_hour = end/100;
    end_min = end%100;
    end = 60*end_hour + end_min;
    dur = end - start;
    hh = dur/60;
    mm = dur%60;
    printf("%02d:%02d",hh, mm);

    return 0;
}